I started double dosing EI values about 2 or so weeks ago on my 750l tank. I knew my co2 uses would go up so I turned my dennerle reg from 6.5 turns to 7.5 turns (cant count bubbles and I cant remember out how to convert to percentages) I've been increasing slowly and am now on 9 turns and still rising (dark green D/C was a yellow colour plus signs of algae). i know co2 varies from tank to tank, but do this large increase sound about right for high fert levels or do i have a fault some where else. the only other thing apart from ferts to change was the addition of some small scabby plants, not even enough to fill a nano. any experience opinions appreciated.